3
这是对this one的后续问题。现在我想在相反方向float - >unsigned int。 以下标量运算的最佳和精确向量序列是什么?将float向量转换为uint32向量的最有效方法?
float x = ...
unsigned int res = (unsigned int)x;
这是对this one的后续问题。现在我想在相反方向float - >unsigned int。 以下标量运算的最佳和精确向量序列是什么?将float向量转换为uint32向量的最有效方法?
float x = ...
unsigned int res = (unsigned int)x;
这是根据从旧但有用苹果的AltiVec-SSE迁移文档不幸的是,现在不再在http://developer.apple.com一个例子:
inline __m128i _mm_ctu_ps(const __m128 f)
{
const __m128 two31 = _mm_set1_ps(0x1.0p31f);
const __m128 two32 = _mm_add_ps(two31, two31);
const __m128 zero = _mm_xor_ps(f,f);
// check for overflow before conversion to int
const __m128 overflow = _mm_cmpge_ps(f, two31);
const __m128 overflow2 = _mm_cmpge_ps(f, two32);
const __m128 subval = _mm_and_ps(overflow, two31);
const __m128i addval = _mm_slli_epi32((__m128i)overflow, 31);
__m128i result;
// bias the value to signed space if it is >= 2**31
f = _mm_sub_ps(f, subval);
// clip at zero
f = _mm_max_ps(f, zero);
// convert to int with saturation
result = _mm_cvtps_epi32(f); // rounding mode should be round to nearest
// unbias
result = _mm_add_epi32(result, addval);
// patch up the overflow case
result = _mm_or_si128(result, (__m128i)overflow2);
return result;
}
http://stackoverflow.com/questions/ 78619 /什么是最快的方式来转换浮点运算在x86上 – Anycorn 2012-02-06 08:34:46
不一样的问题!我想转换为** unsigned ** int – 2012-02-06 08:36:26
你想用负号做什么? – Anycorn 2012-02-06 08:38:42